Along with the recent development of information and communication technology, a variety of wireless communication techniques have been developed. Among them, the WLAN enables a user to wirelessly access the Internet based on radio frequency technology in a home, an office, or a specific service area using a portable terminal such as a Personal Digital Assistant (PDA), a laptop computer, a Portable Multimedia Player (PMP), etc.
To overcome limitations in communication speed that the WLAN faces, the recent technical standards have introduced a system that increases the speed, reliability, and coverage of a wireless network. For example, the Institute of Electrical and Electronics Engineers (IEEE) 802.11n standard has introduced Multiple Input Multiple Output (MIMO) that is implemented using multiple antennas at both a transmitter and a receiver in order to support High Throughput (HT) at a data processing rate of up to 540 Mbps, minimize transmission errors, and optimize data rates.